Tiltable head band saw machine

ABSTRACT

Turning of a hand wheel at the front of a vertical head band saw machine tilts the column thereof on coaxial trunnions which are journaled in bearings on the rear of the saw carriage. The upper and lower saw pulleys are disposed in the plane containing the column tilt axis, with their axles normal to said plane and supported at zones equidistant therefrom by column carried arms that embrace each pulley. One end portion of each axle is detachable to enable a saw band to be trained over its pulley. A motor drives the upper pulley, and band tension is adjusted by bodily movement of the lower pulley, which is weighted to act as a flywheel.

United States Patent Charles E. Cleland MinneapOIisJMinn.

[21] Appl. No. 686,223

[22] Filed Nov. 28, 1967 [45] Patented Jan. 19, 1971 [73] AssigneeContinental Machines, Inc.

Sarage, Minn.

a corporation of Minnesota [72] inventor [54] TILTABLE HEAD BAND SAWMACHINE 10 Claims, 13 Drawing Figs.

[56] References Cited UNITED STATES PATENTS 2,958,347 1 H1960 Blum et a1Primary Examiner-D0nald R. Schran Att0rney-lra Milton Jones ABSTRACT:Turning of a hand wheel at the front of a vertical head band saw machinetilts the column thereof on coaxial trunnions which are journa1led inbearings on the rear of the saw carriage. The upper and lower sawpulleys are disposed in the plane containing the column tilt axis, withtheir axles normal to said plane and supported at zones equidistanttherefrom by column carried arms that embrace each pulley. One endportion of each axle is detachable to enable a saw band to be trainedover its pulley. A motor drives the upper pulley, and band tension isadjusted by bodily movement of the lower pulley, which is weighted toact as a flywheel.

PATENTEUJANIQIQYI 35 1 SHEET 2 OF 7 mam- '51 Ila/and Gin 1 TILTABLE HEADBAND SA W MACHINE The cutting head of such a sawing machine comprises anupright column which is ordinarily supported from the carriage fortilting adjustment about an axis parallel to the path of carriage motionand preferably lying in the horizontal plane of the work supportingsurface on the machine. Cutting is performed by an endless saw bandtrained around a pair of pul leys mounted on the column, one above andthe other below the plane of the work supporting surface. The lowerpulley is 7 power driven, and since both pulleys rotate on horizontalaxes which are normal to the path of carriage motion, the cuttingstretch of the band is ordinarily held twisted 90 by suitable guides, tohave its cutting edge face forwardly, away from the column on which thepulleys are supported.

Heretofore, the mounting of the column on the carriage forside-to-sidetilting adjustmenthas presented serious problems. In orderto assure the desired stability for the cutting head in any of itspositions of adjustment, complicated and costly bearing arrangementswere resorted to even though assembly of the cutting head on the machine.was made more difficult thereby. In some cases, for example, the columnwas tiltably supported by bearings at both the frontand rear of thecarriage, one close to the column and the other a substantial distanceforwardly thereof. This, of course, required the column to have aforwardly extending boomlike structure for cooperation with an arcuatefront bearing. Obviously, the front bearing could not be of aconventional nature if its axis were to lie in the horizontal plane ofthe work supporting surface.

With the foregoing problem in mind, it is a purposeof this invention toprovide exceptionally simple but sturdy means for tiltably mounting thecutting head .of a band saw machine on its carriage.

In this respect, it is a more specific purpose of the invention toprovide the saw supporting column of a band saw machine with coaxialtrunnions that project fore and aft from the column into bearings ontransverse rear portions of the carriage' between which the columnisreceived.

in band saw machines heretofore'available, each of the upper and lowerpulley axles was invariably mounted in cantilever fashion from an arm onthe column,- so as to afford access to one face of its pulley forinstallation of an endless saw band thereon, or for removal of the bandtherefrom. No matter how sturdy the column and the wheel supporting armswere made, tensioning of the saw band trained over the cantilevermounted pulleys caused lateral bowing of the column to a degree thatcould not be tolerated. Fonthat reason, it was customary to provideadjustable bearings for the pulleys, to

enable the latter to be realigned and brought into a common planeparallel to the median plane of the column after the saw band wasproperly tensioned around the pulleys.

In this regard, it is another purpose of the invention to provide acutting head for a bandsaw machine of the character described, whereinboth of the pulleys around which the saw band is trained are mountedwith their peripheries in a common plane which is preferably coincidentwith the median plane of the column, but in any eventiparallel thereto;and wherein each is rigidly supported at both sides of the pulley insuch a way that the tension of a saw band trained around the pulleysdoes not tend to cause lateral bowing or deflection of the column onwhich they are mounted; and the pulleys retain their proper coplanarrelationship, in parallelism with the median plane of the column withtheir axes normal thereto and without need for readjustment of theirbearings after the band is tensioned. t

' rocked in a band tightening direction about its axis.

Still another purpose of the inventionresides in the provi"-" Hence, asto this last described feature. it can be said that it is a purpose ofthis invention to effect a substantial cost reduction through theelimination of expensive adjustable bearing structures for the pulleys,and to simplify the manufacture and the assembly of a sawing machineembodying the invention.

Another and more specific purpose of the invention resides in theprovision of a cutting head for band saw machines of the characterdescribed, featuring a simple but exceptionally rugged mounting for theband wheels or pulleys around which the saw band is trained, whichmounting comprises an axle for each pulley, having opposite end portionssupported by pairs of rigid arms carried by the column and extendingforwardly therefrom at each side of the pulley; and wherein each axlecomprises cooperating axially separable axlc members one of which iscapable of supporting its pulley while the cooperating axle member isdetached therefrom to enable access to be had to one face of its pulleysfor training a saw band thereover or for removal of the band therefrom.

Still another object of the invention resides in the provision of a bandsaw machine of the characterrdescribed, wherein for the first time, theupper of the two band wheels or pulleys is driven from a suitable primemover to achieve a number of advantages heretofore unattainable. Chiefamong these advantages are the simplification of the pulley drive trainand the drive cover design; and location of the drive train in a cleanerarea, above the zone at which sawing takes place.

These desirable features of the invention are made possible to aconsiderable extent by another innovation in band saw machine design,namely the provision of an idler or lower pulley which is weighted toachieve a fly wheel effect that overcomes any tendency for the cuttingstretch of the band, to

vibrate when cutting through a work piece. Such vibration mightotherwise result from the fact that the cutting stretch of the band ispulled through the work by its opposite or non'- cutting stretch, givingrise to somewhat greater elongation of the band during sawing thanobtains when the cutting stretch of the band is pulled through the workby the drive pulley.

A further object of the invention resides in the provision of improvedand simplified means for effecting tensioning of a saw band trained overthe pulleys. Heretofore, this was accomplished by means which involvedmounting the upper pulley on a vertically adjustable bearing, and whichnecessitated costly and accurate machining of close fitting surfaces onthe bearing and guides between which it was slidably received.

In connection with the object of the invention broadly stated in thepreceding paragraph, it is a more specific object of the invention toprovide a cutting head for a band saw machine of the characterdescribed, wherein the lower band' wheel or pulley is rotatablysupported on the outer end of the horizontal arm of a bell crank leverwhich is pivotally mounted on the lower end of the column for rockingmotion about an axis parallel to the pulley axis, andwhich has anupright arm extending upwardly alongside the column and operativelyconnecting with force applying means to enable the lever to b sion ofmeans which is actuatable from the front of the machine for effectingside-to-side tilting adjustment of the cutting head through mechanismconnecting with the rear of its upright column.

With these observations and objects in mind, the manner in' which theinvention achieves its purpose will be appreciated" from the followingdescription and the accompanying drawings. This disclosure is intendedmerely to exemplify the invention. The invention is not limited to theparticular structure disclosed, and changes can be made therein whichlie within the scope of the appendedclaims without departingfromtheinvention.

The drawings illustrate one complete example of the physical embodimentof the invention constructed according to the best mode so far devisedfor the practical application of the principles thereof, and in which:

FIG. 1 is a side elevational view ofa vertical blade band saw machineembodying this invention, portions thereof being broken away to showinternal construction;

FIG. 2 is a front elevational view thereof, indicating in constructionlines the extent of side-to-side tilting adjustment of which the cuttinghead is capable;

FIG. 3 is a sectional detail view, at an enlarged scale, taken on theplane of the line 3-3 in FIG. 1;

FIG. 4 is a cross-sectional view, at an enlarged scale, taken on theline v4-4 in FIG. 1 and showing the mechanism for effecting tilting ofthe cutting head;

FIG. 5 is a sectional detail view taken on the line 5-5 in FIG. 4, andat an enlarged scale;

FIG. 6 is a more or less diagrammatic perspective view showing the drivemechanism for the upper pulley;

FIG. 7 is a fragmentary side elevational view showing how the carriagesupports the cutting head for fore and aft bodily motion therewith andfor side-to-side tilting motion relative thereto;

FIG. 8 is a fragmentary perspective view illustrating the structure seenin FIG. 7;

FIG. 9 is an enlarged detail view partly in section and partly inelevation, illustrating the axle mounting for each pulley;

FIGS. 10. 11 and 12 are diagrammatic views illustrating the bowingeffect of band tension on the cutting head ofa conventional verticalblade band saw machine; and

FIG. 13 is a diagrammatic view similar to FIGS. 10, 11 and 12 butillustrating how the hitherto undesirable bowing effects of band tensionon the column are overcome in the band saw machine of this invention.

Referring now to the accompanying drawings, the numeral 15 generallydesignates the elongated base structure of what can be termed a verticalblade band sawing machine which embodies this invention. Mounted on thetop of the base is a work table 16, the forward portion of which affordsa horizontal work supporting surface 17. Front and rear vises 18 and 19supported on and adjustably securable to the front portion of the tableare adapted to hold a work piece 20 in a fixed position upon the worksupporting surface while a saw cut is made therein or therethrough. Anarrow slot 21 extending fore and aft through the front portion of thetable accommodates the blade 22 of the saw.

Since the saw of this invention is intended primarily as a cutoff sawfor cutting through relatively long work pieces, such as long lengths ofstructural steel, the work table 16 is generally flanked by worksupports 16a and 16b as partially shown in light lines in FIG. 2. Theseflanking work supports usually are quite long and often have powerdriven rollers to advance the work to and carry it from the cuttingzone.

The saw blade 22 is an endless band which is trained around upper andlower band wheels or pulleys 23 and 24, respectively and which, togetherwith an upright column 25 from which the pulleys are supported, comprisethe cutting head 26 of the machine.

The cutting head is mounted upon a U-shaped carriage 27 having oppositeparallel reaches 28 which are horizontally disposed and lie inwardlyadjacent to longitudinal rails 29 fixed to the top of the base 15. Thereaches 28 are rigidly joined together by the bight 30 of the U-shapedcarriage, which bight is located at the rear of the carriage andcomprises a pair of transvers bridge members 31 spaced from one anothera distance to readily receive the column 25 of the cutting headtherebetween. Rollers 32 mounted on the reaches and tracking on edge andside surfaces of the rails 29 constrain the carriage to fore and afttranslatory motion along a horizontal path extending lengthwise of thebase.

The carriage normally occupies a retracted position such as seen in FIG.1, at which its bight 30 is closely adjacent to the rear of the base 15.In the foremost position of the carriage seen in construction lines inFIG. 1, the bight 30 of the carriage will have advanced to a zonesubstantially midway between the ends of the base. The opposite reaches28 of the carriage, of course, are disposed beneath the table 16, nearthe opposite sides thereof.

More or less conventional upper and lower saw guides 34 and 35 arerigidly carried by the column 25 for engagement with the forward orcutting stretch of the saw band 22. While the lower guide 35 can bemounted at a fixed level below the work supporting surface. the upperguide is adjustable up and down in the usual manner. to accommodate workpieces of different heights during sawing. Sawing is accomplished byforward translation of the carriage and the cutting head 26 thereon, butsince the band wheels or pulleys rotate on paral lel horizontal axesnormal to the path of carriage travel, the saw guides must hold theintervening cutting stretch of the saw band twisted with the toothededge thereof facing forwardly, away from the column 25.

One of the features of the band saw machine of this invention resides inthe unusually simple manner in which the cutting head 26 is pivotallysupported by the carriage 27 for side-to-side tilting adjustment out ofvertical, to canted positions necessary for making angled or miter cutsin a work piece. This pivotal support comprises coaxial trunnionsprovided by the end portions of a short shaft 37 which extendshorizontally fore and aft through a central portion of the column 25, towhich it is welded or otherwise secured. These trunnions are journaledin coaxial bearings 38 secured to the transverse bridge members 31,between which the column is received. The bearings 38 provide the solesupport for the cutting head; and since accurate cutting in any and allpositions of the cutting head requires that the plane of the cut made bythe saw always intersects the plane of the work supporting surface 17 onthe same line, the axis of the bearings 38 coincides with the line ofintersection between the cutting plane and the plane of the worksupporting surface. Although this requirement has been met in tiltingtype cutoff saws heretofore available the bearing structures whichdefined the tilt axis in those earlier machines were considerably morecomplicated than the simple bearings of this invention.

Since the column is of tubular construction, being substantiallyrectangular in cross section, it is preferably reinforced by from andrear plates 39 at that portion thereof from which the trunnion definingends of the shaft 37 project. Also, because the main portions of thecarriage are located below the table 16, the bearings 38 are carried bybrackets that are secured by screws to pads 40 on the tops of thetransverse bridge portions of the carriage, and are of a height todispose the axis of the bearings in the plane of the work supportingsurface 17.

The space between the transverse bridge members 31 allows tilting'of thecolumn a full 45 to each side of a normal vertical position, asindicated in FIG. 2. The rear portion of the table, of course, has acentrally located longitudinal cutout 41 therein wide enough toaccommodate the column in any position of adjustment thereof about itstilt axis, and long enough to accommodate the bearings on the carriagethroughout its entire range of fore and aft movement along the base.

The cutting head can be accurately moved to and held in any desiredposition of adjustment on its tilt axis by structure best illustrated inFIG. 4. As therein seen, laterally directed forces can be applied to aportion of the column 25 at a location spaced a distance below its tiltaxis, in consequence of rotation of a screw 43 in one direction or theother. The screw 43 extends transversely and horizontally across therear of the carriage 27, behind the column 25, and has its end portionsjournaled in depending flanges 44 on the carriage by bearings whichpreclude axial motion of the screw relative to the carriage. A nut 45threaded on the screw can be translated lengthwise thereof in onedirection or the other, depending upon the direction the screw isrotated, providing the nut is held against rotary motion with the screw.For this purpose, the nut 45 is pivotally mounted on a stud 46projecting rearwardly from a block 47 which is mounted on the rear ofthe column and constrained to motion lengthwise of the column by ways 48thereon, between which the block is slidably received.

Hence, the stud 46 not only prevents rotation of the nut on the screw43, but it also translates rotation of the screw into slide block 4 7.

55 carried by the baseuA housing'56 having bearings through which thescrew extension 50 andthe'actuating shaft project, serves as anenclosure for the bevel gears 51 and 52' and also holds the same inmeshing engagement as the carriage and the cutting head thereon istranslated fore and aft along the base.

with the structure described above, mechanism at the rear of the columnis operable to adjust the cutting head on its pivot axis inconsequence'of rotation of a'hand wheel at the front of the machine.Precise adjustment of the angle of tilt for beveled cuts is assured byemployingia screw 43 with fine threads thereon; and the tilt angle canbe accurately ascertained by means of a protractor 57 such as indicatedin FIG. 4. It is conventionalin band saw machines of the type hereinconcerned to drive the lower of the t'woband wheels or pulleys aboutwhich thesaw band is trained, and to provide for obtaining the propertension on the saw band byrnaking the bearing for the upper pulleyadjustable up and down with respect to the column from whichit issupported. The presentinvention departs from the conventional in theserespects in that it provides for band tensionirrg adjustment 'of thelower pulley 24 and for driving the upper pulley 23; to achieve certainsignificant advantages which will appear shortly. s

The upper pulley 23 is driven from a prime mover 8 which is mounted inanenclosure 59 that issecured to the column at a location near the levelof the upper pulley. The prime mover can bean electric motor having amultiple V-groove drive sheave 60 on its shaft 61. The drive sheave 60is located adjacent to one side'of the column 25,1rearwardly in linewith another multiple groove sheave 62 which is fixed to one end of ashort shaft 63 extending across the front of the column. The

shaft 63 is journaled inabearing 64 on thejfront of the column forrotation on a horizontal axis parallel .to thatof the motor shaft 61. AV-belt 64 engaged in "selected grooves in the sheaves 60 and 62drivingly connects the shaft 63 with the mo (01. i

Fixed to the other end-of the shaft 63, at the opposite side of thecolumn 25, is another sheave 65. which is drivingly connected by a belt66 with a largersheave 67 fixedto one end of a pulley drive shaft68.;The pulley drive. shaft is supported from the column 25 for rotationon a transverse axis parallel to and coplanar with the axis of the upperpulley 23, just behind its periphery. A more specific reference will bemade later to the manner in which the pulley drive shaft 68 is supporteda larger gear 70 on the flanged periphery of the upper pulley 23. Theusual housing structure 71 encloses the upper pulley and all of itsdrive train except the belt 64 trained over the motor sheave 60. Thislast named belt can be housed within the motor enclosure 59. V

In the pulley drive arrangement described, the forward or cuttingstretch of the saw band is moved downwardly during sawing in consequenceof the pull which the power driven upper pulley exerts upon both thecutting and the noncutting stretches of the saw band. Since the saw bandis, in effect, a spring that stretches under load, the increased lengththrough which the pull on its cuttingstretch is exerted can tend tocause vibrations which cannotbe tolerated. In order to overcome anytendency for such vibration, this invention provides a lower band wheelor pulley 24 which is weighted to an extent sufficient that itsincreased mass and inertia enables it to achieve a flywheel effectduring sawing-Thus, the tension can be maintained substantially uniformon the cutting stretch of the blade. and vibration is effectivelyprecluded.

A simple shielding device 73 can be applied over the lower pulley 24 toprotect it from metal shavings producedduring sawing. It should benoted, however-(that. the power driven pulley 23 and its drive mechanismare located in a clean area. a distance above the cutting zone, where nospecial shielding is required. s

According to this invention, the band wheels or pulleys 23 and 24 aresupported by structure that is vastly superior to the conventionalcantilever supporting meansheretoforc employed in band sawing machinesof thisnaturefSuch conven pulleys, to bring the latter into edgewisealignment and" thereby compensate for the lateral bowing" or distortionthat occurred in the column as a result of band tension. This conditionisdiagrammatically illustrated in FIGS. 10. I1 and 12, which represent atypical cantilever mounting of the upper and lower band wheels orpulleys 23 and 24 in adjustable bearings B on one side of arms Aextending forwardly from the column v s i FIG. 10 illustrates. thestraight condition of the column C and the edgewise alignment of theupper and lower pulleys that obtainsbefore the saw band22' is tensioned.When the band is properly tensioned, its pull upon the offset pulleyscauses the column Cto bow or deflect laterally as illustrated inexaggerated form in FIG. 11, so that the axes of the upper and the lowerpulleys are no longer parallel and the pulleys are out of the edgewisealignment desired. It is at this time that the bearingsB for thepulleysmust be adjusted relative to the columnfas indicated in FIG. 12,to bring the axes of the pulleys back into parallel relationship, Itwill be apparent. therefore, that special and costly adjustable hearingswere essential in conventional band saw machines; and that considerabletime had to be spent in tedious readjustment of the bearings each timeit was necessaryto replace a band, and especially if the new band was ofdifferent width or cutting characteristics,

requiring a different tension load.

FIG. 13 diagrammatically illustratesthe mounting for the band wheels orpulleys in the sawing machine of this invention, which, mounting is suchas to eliminate the tendency for the column to bow laterally under thetension of the saw band upon the pulleys. As will now be described, thisfeature of the invention is achieved by rigidly supporting the pulleys23 and 24 at their opposite sides,,with their peripheries in a commonplane which may be coincident with the median plane of the column 25,but in any event is parallel thereto. Specifically each pulley isjournaled on an axle 77 that is jointly carried by a pair of rigidspaced apart parallel arms 75 and 76 that roject forwardly from thecolumn, Each pair of arms embraces one of the pulleys.

If the arms of each pair are equispaced from the common plane of thepulleys and also equidistant from the median plane of the column, as isthe case in the embodiment of the invention illustrated in the drawings,the pulley supporting have to have the same moment of inertia.Obviously, though,

the arms need not be symmetrical to the median plane of the column. Theonly important consideration is that the pulley supporting structures atthe opposite sides of the pulleys be designed to carry their share ofthe band tension load imposed thereon. In other words, if the supportingstructures are not equidistant from the median plane of the column andthe plane of the pulleys, so that the loads imposed thereon by 1 bandtension are not equal, this difference in loading can be compensated bydesigning the supporting structures with correctly calculated differentmoments of inertia-the supporting structure at one side of the pulleywould simply have to be stronger than the other.

In any event, the band tension load on the pulleys is so divided betweenthe pulley supporting structures at the opposite sides thereof, that nolateral deflection or bowing of the column takes place and the pulleyaxes remain parallel.

The arms 75 76 between which the upper pulley is mounted, can bestraight flat bars having their rear end portions flatwise overlying theopposite sides of the column and rigidly fixed thereto as by welding.They project horizontally forwardly from the column, to opposite sidesof the upper pulley 23, and their outer end portions are apertured toreceive and support the opposite end portions of the upper pulley axleThe upper arms 7576 also provide supports for the pulley drive shaft 68,which projects through them and is rotatably journaled in suitablebearings carried thereby (see FIG. 1).

Though FIG. 9 shows the mounting for the lower pulley 24, the axles forboth pulleys are substantially identical. Each axle is comprised ofcooperating axially separably connected main and secondary axle members78 and 79 respectively. The main axle member 78 is stepped to provide alarger diameter end portion 79 which projects axially from one side ofthe pulley through a hole 80 in the adjacent arm'75 to a flange 81 onits outer end. The flange 81 can be integral with the main axle member,and it is secured as by screws 82 to the outer face of its supportingarm so as to rigidly mount the main axle member thereon.

The smaller diameter inner portion 83 of the main axle member 78projects through the hub 84 of the pulley and receives ball bearings 85by which the pulley is freely rotatably supported by the main axlemember. One of the bearings abuts the shoulder 86 at the junctionvbetween the smaller and larger diameter portions of the main axlemember, and a spring ring 87 snapped into a suitable groove in theextremity of the smaller diameter axle portion83 cooperates with theshoulder 86 to prevent axial movement of the pulley relative to theaxle.

The end portion of the main axle member which is encircled by the pulleyis hollow and provides an axially elongated socket 89 to snugly butrotatively receive a reduced end portion 90 on its cooperating secondaryaxle member 79. Screw threads 91 formed on the extremity of the reducedportion 90 and cooperating with complementary threads in the bottom'ofthe socket 89 hold the main and secondary axle members assembled, withashoulder 92 on the secondary axle member engaging the extremity of thesmaller diameter portion 83 of the main axle member.

The secondary axle member 79 extends axially outwardly through a hole 93in its adjacent arm 76 to thus receive support therefrom. A handle 94fixed to the secondary axle member and accessible from the exterior ofits arm 76 facilitates rotation of the secondary axle member in thedirection to effect axial separation thereof from the'main axle memberat times when access must be had to the pulley to train the saw bandthereover or to remove the band therefrom.

It should be observed that the pulley supporting arms 75 which carry themain axle members 78 are strong and rigid enough to alone bear the loadof band tension on the pulleys and thereby prevent damage to the machinein the event an operator inadvertently fails to replace the secondaryaxle members before tensioning the saw band on the pulleys. Though thiswill prevent damage to the machine, it will not necessarily assure theedgewise alignment of the-pulleys essential to keep the saw band runningtrue. As a result; this omission will be quickly detected by theoperator, and corrected by replacement of the secondary axle members 79.

The lower pulley'24 isbodily adjustable up and down, so that the sawband can be tensioned in consequence of downward movement thereof. Forthis purpose, it is supported by a bell crank lever 96, of which theopposite arms 75 and 76 described earlier form a part. The arms 75 and76 of the bell crank lever project substantially horizontally fromopposite sides of the column to which they are pivotally connected by astub shaft 97. The bell crank lever also comprises opposite upright arms98 which are rigidly connected to the pivoted at 102 so that rotarymotion of the wheel in one directioncauses counterclockwise pivotalmotion ofthe bell crank lever and tensioning of a saw band trainedaround the pulleys. Ro-

tary motion of the hand wheel in the opposite direction, of crankcourse. effects clockwise swinging motion of the bell lever to relax thetension of the saw band. 1

From the foregoing description, together with the accompanying drawings,it will be readily apparent to those skilled in not only constitutes asubstantial improvement over the conventional, but which is also simplerand less costly.

lclaim:

l. A sawing machine having a base with a flat surfaced work.

supporting table the front portion of which is slitted to accom the artthat this invention provides a band saw machine which modate the cuttingstretch of a saw band. and a carriage hav ing front and rear portionsand constrained to fore and aft translatory motion on the basealong apath lengthwise of the slit in its work supporting table, said machinebeing charac-, terized by:

A. a pair of spaced apart rigid front and rear members at the a rearportion of the carriage and extending transversely'of its path ofmotion, both of said members being rearwardly of the slitted frontportion of the work supporting table in all positions of the carriage;B. a cutting head on the carriage movable bodily fore and aft therewith,said cutting head comprising a column having a portion intermediate itsends accommodated in the space between said transverse members, and asaw blade- I having a cutting stretch disposed ahead of the foremost ofsaid spaced apart members and substantially parallel to the column withits cutting edge facing forwardly to travel along the slit in the worksupporting table during fore and aft movement of the carriage; I C.coaxial trunnions projecting horizontally fore and aft from the column;

D. and bearings on said transverse members in which said trunnions. arejournaled, said bearings supporting the cutting head for tiltingadjustment relative to the-carriage about a horizontal axissubstantially coincident with the plane of the flat work supportingsurface of the table and parallel to the path of motion of the carriage,and each of said bearings completely encircling the trunnion therein sothat throughout its range of tilting adjustment the cutting head isuniformly supported against any lateral as wellas downward forecesacting thereon. v 2. The sawing machine of claiml further characterizedby saw guiding means constraining the cutting stretch of the saw' bladeto travel in a plane which intersects theplane of thework supportingsurface and also contains the'tilt axis.

3. The sawing machine of claim 1 wherein said carriage is" substantiallyU-shaped to provide a bight at its rear which is comprised of saidtransverse members, and widely spaced apart arms which project forwardlyfrom the bight.

4. The sawing machine of claim 1 further characterized by: 9

A. the saw blade comprising an endless flexible saw band;

B. a pair of pulleys carried by the column and about, whichj the sawband is trained, said pulleys being rotatable about axes which'aredisposed transversely of the-path of the fore and aft motion of thecarriage, one of said pulleys 7 being located a distance above thecarriage and theother being located below the carriage; C. and means fordriving the upper one of said pulleys.

5. The sawing machine of claim 1 further characterized by means forimparting side-to-side tilting motion tothe cutting head, comprising:

A. an elongated screw mounted on and extending transversely across thecarriage at a location below thetilt axis for t the cutting head, andconstrained to rotate on a horizontal axis adjacent to a portion of saidcolumn;

B. a nut threaded on said screw; a

C. a member mounted on the column and constrained to translating motionlcngthwise thereof;

D. means pivotally connecting said member with the nut whereby rotationof the screw effects tilting of the column on the axis of its trunnionsin a direction depending upon the direction the screw is turned;

E. and actuator means drivingly connected with the screw to provide forthe transmission of rotary movement thereto. V

6. The sawing machine of claim '5,wherein said actuator means comprises:1

A. an elongated actuator shaft rotatably carried by the base andextending from the front to the rear thereof;

B. a hand wheel fixed to the front of the actuator shaft;

C. and meshing bevel gears on the actuator shaft and the screw, the gearon the actuator shaft having a splined driving connection therewith toallow the gears to remain in mesh during back and forth motion of thecarriage.

7. A cutting head for a band saw machine comprising upper and lowerpulleys carried by an upright column and rotatably on parallelhorizontal axes spaced a distance forwardly of the column, and anendless flexible saw band trained around said pulleys, said cutting headbeing characterized by:

supporting structure for each pulley by which the pulleys are held withtheir axes parallel. and in edgewise vertical alignment and lying on aplane parallel with a vertical median planethrough the columnhth'esupporting structure for each pulley comprising:

l. a pair of substantially opposite armsembracing the pulley, both ofsaid arms projecting rearwardly to the column and havingforcetransmitting connections therewith at opposite sides of said medianplane;

2. an axle by which the pulley is rotatably connected with the arms, theaxle projecting from each side of the pulley and being supportinglyconnected at its opposite end portions with the arms, so that the axleof each pulley has a force transmitting connection with the column ateach side of said median plane, and

said supporting structure beingfurther characterized in that; thespacing of the arms from the opposite sides of the pulleys and theirrespective moments of inertia are such that the band tension load on thepulleys is so divided between the pulley supporting structures at theopposite sides of the pulleys that nolateral deflection or bowing of thecolumn takes place and the pulley axes remain parallel.

8. The cutting head of claim 7. wherein each of said axles comprises: I

A. a main axle member rigidly connected to one of its supporting arms;

B. a cooperating secondary axle member coaxial with the first axlemember;

C. means axially separably connecting said main and secondary axlemembers together;

D. and the pulleys being rotatably journaled on said main axle membersto be supported thereby at times when the secondary axle members aredetached from their respective main axle members.

9. The cutting head of claim 8 further characterized by means on each ofsaid main axle members precluding axial movement of its pulley relativethereto so as to prevent displacement of said pulley at times when thecooperating secondary axle member is detached from its main axle member.

10. In a band saw machine having'an endless flexible sawband trainedaround spaced upper and lower pulleys that rotate on parallel axes,means supporting said pulleys comprising:

A. an upright column;

B. a pair of rigid spaced apart opposing arms carried by and projectingsubstantially horizontally forwardly from each end plgortion of thecolumn; C. a hu on each pulley, disposed in the space between each pairof arms;

D. axle means extending through the hub of each pulley and having endportions supportingly carried by the arms at each side of said hub, thearms and axle means mounting the pulleys with their peripheral portionssubstantially symmetrical fore and aft with the median plane of thecolumn;

E. said axle means for each pulley comprising a main axle member rigidlyfixed to one of the supporting arms for said pulley, and a secondaryaxle member axially slidably mounted in a hole in the opposite arm andhaving an axially separable screw threaded c'onnection with the mainaxle member, the pulley being mounted on the main axle member so that itis supported solely'thereby when said secondary axle, member isdetached; and

F. each pulley being spaced from the arm supporting its secondary axlemember a distance toenable an endless saw band to be trained around itspulley and/or removed therefrom when said secondary axle member isdetached from its main axle member.

1. A sawing machine having a base with a flat surfaced work supportingtable the front portion of which is slitted to accommodate the cuttingstretch of a saw band, and a carriage having front and rear portions andconstrained to fore and aft translatory motion on the base along a pathlengthwise of the slit in its work supporting table, said machine beingcharacterized by: A. a pair of spaced apart rigid front and rear membersat the rear portion of the carriage and extending transversely of itspath of motion, both of said members being rearwardly of the slittedfront portion of the work supporting table in all positions of thecarriage; B. a cutting head on the carriage movable bodily fore and afttherewith, said cutting head comprising a column having a portionintermediate its ends accommodated in the space between said transversemembers, and a saw blade having a cutting stretch disposed ahead of theforemost of said spaced apart members and substantially parallel to thecolumn with its cutting edge facing forwardly to travel along the slitin the work supporting table during fore and aft movement of thecarriage; C. coaxial trunnions projecting horizontally fore and aft fromthe column; D. and bearings on said transverse members in which saidtrunnions are journaled, said bearings supporting the cutting head fortilting adjustment relative to the carriage about a horizontal axissubstantially coincident with the plane of the flat work supportingsurface of the table and parallel to the path of motion of the carriage,and each of said bearings completely encircling the trunnion therein sothat throughout its range of tilting adjustment the cutting head isuniformly supported against any lateral as well as downward forecesacting thereon.
 2. The sawing machine of claim 1 further characterizedby saw guiding means constraining the cutting stretch of the saw bladeto travel in a plane which intersects the plane of the work supportingsurface and also contains the tilt axis.
 2. an axle by which the pulleyis rotatably connected with the arms, the axle projecting from each sideof the pulley and being supportingly connected at its opposite endportions with the arms, so that the axle of each pulley has a forcetransmitting connection with the column at each side of said medianplane, and said supporting structure being further characterized inthat; the spacing of the arms from the opposite sides of the pulleys andtheir respective moments of inertia are such that the band tension loadon the pulleys is so divided between the pulley supporting structures atthe opposite sides of the pulleys that no lateral deflection or bowingof the column takes place and the pulley axes remain parallel.
 3. Thesawing machine of claim 1 wherein said carriage is substantiallyU-shaped to provide a bight at its rear which is comprised of saidtransverse members, and widely spaced apart arms which project forwardlyfrom the bight.
 4. The sawing machine of claim 1 further characterizedby: A. the saw blade comprising an endless flexible saw band; B. a pairof pulleys carried by the column and about which the saw band istrained, said pulleys being rotatable about axes which are disposedtransversely of the path of the fore and aft motion of the carriage, oneof said pulleys being located a distance above the carriage and theother being located below the carriage; C. and means for driving theupper one of said pulleys.
 5. The sawing machine of claim 1 furthercharacterized by means for imparting side-to-side tilting motion to thecutting head, comprising: A. an elongated screw mounted on and extendingtransversely across the carriage at a location below the tilt axis forthe cutting head, and constrained to rotate on a horizontal axisadjacent to a portion of said column; B. a nut threaded on said screw;C. a member mounted on the column and constrained to translating motionlengthwise thereof; D. means pivotally connecting said member with thenut whereby rotation of the screw effects tilting of the column on theaxis of its trunnions in a direction depending upon the direction thescrew is turned; E. and actuator means drivingly connected with thescrew to provide for the transmission of rotary movement thereto.
 6. Thesawing machine of claim 5, wherein said actuator means comprises: A. anelongated actuator shaft rotatably carried by the base and extendingfrom the front to the rEar thereof; B. a hand wheel fixed to the frontof the actuator shaft; C. and meshing bevel gears on the actuator shaftand the screw, the gear on the actuator shaft having a splined drivingconnection therewith to allow the gears to remain in mesh during backand forth motion of the carriage.
 7. A cutting head for a band sawmachine comprising upper and lower pulleys carried by an upright columnand rotatably on parallel horizontal axes spaced a distance forwardly ofthe column, and an endless flexible saw band trained around saidpulleys, said cutting head being characterized by: supporting structurefor each pulley by which the pulleys are held with their axes parallel,and in edgewise vertical alignment and lying on a plane parallel with avertical median plane through the column, the supporting structure foreach pulley comprising:
 8. The cutting head of claim 7, wherein each ofsaid axles comprises: A. a main axle member rigidly connected to one ofits supporting arms; B. a cooperating secondary axle member coaxial withthe first axle member; C. means axially separably connecting said mainand secondary axle members together; D. and the pulleys being rotatablyjournaled on said main axle members to be supported thereby at timeswhen the secondary axle members are detached from their respective mainaxle members.
 9. The cutting head of claim 8 further characterized bymeans on each of said main axle members precluding axial movement of itspulley relative thereto so as to prevent displacement of said pulley attimes when the cooperating secondary axle member is detached from itsmain axle member.
 10. In a band saw machine having an endless flexiblesaw-band trained around spaced upper and lower pulleys that rotate onparallel axes, means supporting said pulleys comprising: A. an uprightcolumn; B. a pair of rigid spaced apart opposing arms carried by andprojecting substantially horizontally forwardly from each end portion ofthe column; C. a hub on each pulley, disposed in the space between eachpair of arms; D. axle means extending through the hub of each pulley andhaving end portions supportingly carried by the arms at each side ofsaid hub, the arms and axle means mounting the pulleys with theirperipheral portions substantially symmetrical fore and aft with themedian plane of the column; E. said axle means for each pulleycomprising a main axle member rigidly fixed to one of the supportingarms for said pulley, and a secondary axle member axially slidablymounted in a hole in the opposite arm and having an axially separablescrew threaded connection with the main axle member, the pulley beingmounted on the main axle member so that it is supported solely therebywhen said secondary axle member is detached; and F. each pulley beingspaced from the arm supporting its secondary axle member a distance toenable an endless saw band to be trained around its pulley and/orremoved therefrom when said secondary axle membEr is detached from itsmain axle member.